Interest in the potential of OLED device technology has been driven in large part by the demonstration of flat panels that have highly-saturated colors and have high contrast, and that are ultrathin and energy efficient. Additionally, a wide variety of substrate materials, including flexible polymeric materials, can be used in the fabrication of OLED devices. An OLED device can be manufactured by the printing of various organic and other thin films onto a substrate using an industrial printing system. Nearly any desired size of substrate can be used in such a process, from substrates sized for use as cell phone displays to substrates sized for use as very large television (“TV”) screens. To provide two non-limiting example, ink jet printing of thin films can be used for Gen 7.5 substrates, having dimensions of about 195 cm×225 cm, with these substrates then being cut into eight 42″ or six 47″ flat panels per substrate, and for Gen 8.5 substrates, having dimensions of about 220×250 cm, with these substrates then being cut into six 55″ or eight 46″ flat panels per substrate.
OLED devices typically have a number of pixels that make up a display. In a color display, each pixel typically has three separate color generating elements. Each of these elements, in turn, typically uses a “well” to receive one or more thin film layers during an ink jet printing process. Thus, each pixel of the OLED device is typically associated with three wells corresponding to respective pixel colors. The assemblage of layers for each color component (i.e., associated with each well) forms an “OLED stack.” Each OLED stack can include 6-7 film layers. During manufacture, it is desired to uniformly deposit each of these layers.
For perspective, a high-definition flat panel display can contain over 2 million pixels with a pixel density of between about 300 ppi to about 450 ppi. Clearly, given the sheer number of functioning pixels that must be formed on a substrate during manufacture of various OLED devices, a high degree of manufacturing accuracy is required. In the process of forming the various layers, various discontinuities between or within film layers can occur, which can result in a pixel that does not perform as designed or is otherwise identified as defective.
Accordingly, there is a need in the art for systems, devices and methods that can be used to timely and systematically assess quality of thin films formed on a substrate during the manufacture of an OLED device.